The present invention relates to methods for automatically determining the type and amount of plotting media provided on a supply tube and, more particularly, to a scheme for determining the type and amount of plotting media on a hollowtubed media supply tube by using a barcode strip secured to the inner surface of a plotting media tube which is continuously optically scanned by an optical scanning probe inserted into the plotting media supply tube while the plotter is in operation.
Currently, methods for allowing a plotter to differentiate between different media types include: entering information into the plotter's driver software (within the computer to which the plotter is attached), entering information directly into the plotter via a plotter configuration menu, or adjusting the plotter's dip-switches. Knowing the type of plotting media presently in use allows the plotter to incorporate the particular media's thickness into a calculation to determine the amount of media remaining on the media supply tube. Present methods for determining the amount of media on a media supply tube include marking the borders of the last remnants of media with colored ink, or using the physical presence of the plotting media to restrain a mechanical sensor or block an optical light source within the plotter's media handling mechanism. These methods are only useful in determining when the media supply tube is empty and cannot be used to determine the amount still remaining. Simply using the rotational velocity of the supply tube without knowing the thickness of the particular media does not allow for precise quantity calculations, only rough estimates. Furthermore, knowing the media's identity allows the plotter to handle the media in a manner consistent with its particular characteristics. Delicate forms of plotting media may require careful handling and slower pen carriage speeds, while sturdy media can be handled vigorously. Some media types (such as transparencies whose smooth surface is easily marked) are conducive to high pen speeds.
The marking of containers containing different web media is known in the art. Film containers are a primary source of such prior art. For example, East German Patentschrift 51533 shows a film cartridge having a series of dot positions on the cartridge side portions which can be used to indicate the film speed. French 1451597 accomplishes the same result by placing the dot positions radially on the cartridge end. U.S. Pat. No. 3,490,348 replaces the dots of French 1451597 with mechanically sensible raised or indented radial arcs at various radii and/or positions to indicate the film attributes. U.S. Pat. No. 3,276,340 simply put positioned notches in the rim of the metal film cartridge for the same purpose.
More recently and of more pertinence to the present invention, Yamamoto in U.S. Pat. No. 4,920,376 provided a cartridge for a photosensitive recording medium in which information about the recording medium in the cartridge is printed in bar-code format on the outside of the cartridge.
In any web media, placing the media in a cartridge adds to the complexity of the using apparatus as well as the cost of the media. For example, in Yamamoto there must be space for the cartridge as well as optical apparatus for scanning the bar code.
In roll-fed plotters, it is desirable to simply provide the plotting media rolled on a cardboard supply tube. On the other hand, it is also desirable to be able to provide more detailed information about the media on the supply tube than can be encoded into notches or dots on the end of the cardboard tube.
Wherefore it is an object of this invention to provide a scheme for automatically determining the precise type and amount of plotting media on a particular plotting media supply tube loaded into a plotter.
It is another object of this invention to provide methods and apparatus for simply and efficiently marking a cardboard media supply tube with barcoded information and subsequently reading it at a time of use.
Other objects and benefits of the invention will become apparent from the detail description which follows hereinafter when taken in conjunction with the drawings and figures which accompany it.